In general, electrophotographic image forming apparatus (such as printers, copiers and facsimile machines) are configured to irradiate (expose) a charged photoconductor with laser light according to the image data to form thereon an electrostatic latent image, and deposit colored particles, or toner, on the electrostatic latent image, visualizing the electrostatic latent image to form a toner image. The toner image is then directly or indirectly transferred onto a sheet, and heated and pressurized by a fixing device for fixation to form an image on the sheet.
The fixing device includes a fixing-side member (e.g., fixing roller or belt) that comes into contact with an image-formation side of the sheet, and a reverse-side supporting member (e.g., pressing roller or belt) that comes into contact with the reverse side (i.e., the side opposite to the image-formation side) of the sheet by being pressed against the fixing-side member with a predetermined load. The reverse-side supporting member is pressed against the fixing-side member to thereby form a nip portion that holds and carries a sheet.
In such a fixing device, during fixing of the toner image to the sheet, adhesion of melted toner may cause the sheet to wind around the fixing-side member, which may result in fixing failures such as paper jam. Recently, in particular, the diameter of the fixing roller has been increased to secure sufficient nip time for accelerated fixing. In this case, however, the resultant smaller curvature at the exit of the nip portion makes it difficult to separate the sheet.
Consequently, there has been proposed a fixing device that includes an air separation section that blows air toward the leading end of the sheet that has passed through the nip portion, in order to separate the sheet winding around the fixing-side member. A compressor-type air separation section including an air supply source with a compressor (compression machine) has been known (see, e.g., Patent Literature 1). The compressor-type air separation section can blow compressed air at a larger discharge pressure than a fan-type air separation section, and thus can reliably separate the sheet even when a pliable sheet is used or even when the volume of deposited toner is large.
Patent Literature 1 discloses an image forming apparatus configured to disable a compressor (i.e., configured to inhibit the generation of compressed air) during image formation in order to prevent reduction of image quality caused by the compressor's vibration propagated to image forming sections.